A process for separating carbon monoxide from a feed gas containing CO, CO.sub.2 and N.sub.2 by using PSA in a two-stage adsorption process is disclosed in U.S. Pat. No. 4,539,020 dated Sept. 3 1985 by Sakuraya et al. According to the process disclosed therein, as the concentration of CO in the feed gas changes, the concentration of CO in the product gas also changes.
A problem in using waste gas from a converter furnace as a starting material for a chemical process is that the concentration of CO in the waste gas changes with time. Therefore, it is difficult to continously obtain a Product having a substantially constant concentration of CO. The converter waste gas typically contains CO in a concentration of from about 70 to 80%. From this gas, CO with a purity of about 98% can be produced. However, the concentration of CO in the converter gas will sometimes fall to about 50% and the purity of CO in the product gas will correspondingly fall to 96-97%. Where the product gas is utilized directly in a chemical process, such a drop in the concentration of CO therein may result in a stoppage of the reactor. If, on the other hand, the apparatus is designed to utilize the lowest concentration of CO typically found in waste gases, e.g. 50%, a significant amount of power will be wasted when the feed contains typical levels of 70-80% CO.